Apparatus for remote ignition of explosives

ABSTRACT

Disclosed herein is a unique non-electric ignition device for sounding rockets, explosives or the like which involves energization of a fluidic conversion device embedded in the explosive charge to be ignited. The fluidic device, consisting essentially of a convergent nozzle and resonance tube, is connected through pneumatic tubing to a remotely located pump, valve, filter network. When operated, this network develops a pre-ignition pressure level which eventually reaches a threshold level sufficient to open a relief valve. At threshold the pressurized gas is applied to the convergent nozzle, which directs the gas toward the opening of the resonance tube. A system of self-sustaining oscillations of the gas particles is created in the tube which causes the closed end of the tube to rise in temperature. The end of the tube is surrounded by a pyrotechnic-ignition interface which ignites when the tube end temperature reaches a predetermined level. This interface then ignites the main propellant resulting in the firing of the sounding rocket, detonation of the explosive, or the like.

United States Patent Marchese et a1.

[11] 3,811,359 [451 May 21,1974

1 1 APPARATUS FOR REMOTE IGNITION OF EXPLOSIVES The Singer Company,Little Falls, NJ.

Filed: Dec. 18, 1972 Appl. No.: 316,132

[73] Assignee:

US. Cl 89/l.8l3, 89/7, 102/49.7 Int. Cl F4lf 3/04 Field of SearchlO2/49.7, 25; 89/l.8l3,

References Cited UNITED STATES PATENTS 12/1971 Rakowsky 89/7 6/1972Axelson 102/16 6/1973 Allport 124/ll R 7/1962 Butler et al. 124/11 R12/1971 Rakowsky 89/7 3/1963 Reynolds et al. 102/25 PrimaryExaminer-Samuel W. Engle Attorney, Agent, or Firm-T. W. Kennedy [57]ABSTRACT Disclosed herein is a unique non-electric ignition device forsounding rockets, explosives or the like which involves e nergization ofa fluidic conversion device embedded in the explosive charge to beignited. The fluidic device, consisting essentially of a convergentnozzle and resonance tube, is connected through pneumatic tubing to aremotely located pump, valve, filter network. When operated, thisnetwork develops a pre-ignition pressure level which eventually reachesa threshold level sufficient to open a relief valve. At threshold thepressurized gas is applied to the convergent nozzle, which directs thegas toward the opening of the resonance tube. A system ofself-sustaining oscillations of the gas particles is created in the tubewhich causes the closed end of the tube to rise in temperature. The endof the tube is surrounded by a pyrotechnic-ignition interface whichignites when the. tube end temperature reaches a predetermined level.This interface then ignites the main propellant resulting in the firingof the sounding rocket, detonation of the explosive, or the like.

11 Claims, 4 Drawing Figures PATENTEMAY 2 I I974 SHEET 1 OF 2 FIG.1

PATENTEDHAY 2 1 I974 SHEEI 2 (IF 2 FIG.2

J +4-CELLI I CELLE I APPARATUS FOR REMOTE IGNITION OF EXPLOSIVESBACKGROUND OF THE INVENTION The invention described herein was made inthe performance of work under a NASA Contract and is subject to theprovisions of Section 305 of the National Aeronautics and Space Act of1958, Public Law 85:568 (72 Stat. 435; 42 U.S.C. 2457).

This invention relates to an explosive igniting device, and moreparticularly to a device for igniting explosives wherein a fluidicdevice converts the energy stored in a remotely connected pressuresystem to thermal energy and to thereby ignite the explosivecomposition.

Sounding rockets which are low cost rockets used by various governmentalagencies to determine the meteorological conditions in the upperatmosphere are typically propelled to these heights by solidpropellants. These relatively small rockets (approximately 7 feet high)can be moved about and fired by a single operator. Telemetric deviceslocated in the payload section of these rockets sense and transmit backto earth meteorological information useful for the navigation ofaircraft in the area, suitable for assisting in the determination of thehigh altitude trajectory of land-launched missiles or manned spaceflights, and other obvious applications.

The ignition system which initiates the firing of these rockets ideallymust be inexpensive, safe, reliable, and relatively foolproof. In thepast, some form of electroexplosive technique was employed. Thisinvolved the connection of electrical wires to the propellant igniter,which in turn was connected to a source of electrical energy such as agenerator or battery. Alternately, radio frequencies might be generatedwhich would trigger an appropriate receiving device located in thepropellant igniter section which, responding to the transmitted radiowaves. would generate intense heat, which in turn would ignite thepropellant. These prior art ignition techniques suffer from aparticularly serious safety deficiency. They are susceptible tounintentional ignition through sources beyond the control of theoperator. Things such as electrostatic charge buildup, lightning. radiotransmitters in passing autos or aircraft, or other electromagneticfield generating devices can, if generating sufficient energy in thearea of the sounding rocket, ignite the propellant to thereby cause anunintentional firing of the rocket. This, of course, has ominousconsequences.

A recent development by the assignee of this application in the area ofbasic fluidic to thermal conversion devices, such as that described inUS. Pat. No. 3,630,150 and 3,360.15 I. has enabled the development of anignition device which eliminates the unintentional firing of the rocket.making it strictly the operator who controls when the rocket is to befired.

SUMMARY OF THE INVENTION It is. therefore. the object of this inventionto provide a non-electric. fluidic ignition device for a remotelylocated explosive charge.

It is a further object of this invention to provide an ignition devicewhich may not be initiated unintentionally.

It is a further object of this invention to provide an ignition devicewhich uses the surrounding air as the initiating fluidic agent.

A non-electric system for remote ignition of an explosive charge whichincludes in combination, an energy source for developing a supplypressure of a predetermined level, a fluidic conversion device connectedto the energy source through a fluidic network which includes checkvalves, a line filter, pneumatic tubing and a relief valve, whereupon inresponse to the opening of the latter due to the supply pressureexceeding the predetermined level, the fluidic device converts thepressure waves emanating from the relief valve into thermal energy whichin turn ignites a pyrotechnicexplosive charge suitable to ignite themain propellant or explosive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1: A simplified, pictorialdrawing of the invention as used in a sounding rocket.

FIG. 2: A detailed drawing of the energy source and connecting fluidicnetwork as used in the subject invention.

FIG. 3: A detailed sectional view of the fluidic conversion device whichforms part of this invention.

FIG. 4: A schematic view of the static pressure distribution at the exitof the nozzle of the fluidic conversion device in FIG. 3.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIG. I, there isshown in combination the functional-elements which comprise thesubstance of this invention. A source of energy," an air pump 10, isshown connected to a length of pneumatic tubing 12, through a valve,filter arrangement 14. The pneumatic tubing 12 is connected to a reliefvalve l6 which is calibrated 'to open at the threshold operatingpressure for the fluidic conversion device 18. In this illustration, thefluidic conversion device is shown set in a sounding rocket 20, but itis to be understood that this may as easily be any explosive device,even such as dy-. namite. The relief valve 16 is connected to thefluidic device 18 through an additional length of pneumatic tubing 22.The fluidic device 18 is embedded in the main propellant 24, and inaccordance with the principals of operation for the fluidic device 18,is vented to the outside atmosphere through venting tube 26.

Referring now to FIG. 2, a more detailed description of the energysource, valve filter arrangement, and relief valve may be discussed. Allof the parts depicted in FIG. 2 are essentially of a standard nature butare configured in the arrangements of FIG. 2 so as to enable a humanoperator to raise the level of the air pressure at the exhaust port 28,which is connected to the input of the fluidic device 18 through tubing22, to a level of air pressure suitable for igniting the propellant 24when the fluidic device 18 converts the air pressure to thermal energy.A suitably sized pump 10, easily operated by a human operator typicallymight have a bore diameter d, of 35 mm with a 51 cm stroke. The exitport 30 of pump 10 is coupled to the exhaust port 31 of check valve 32through coupling 34. The check valve 32 has an intake port 36.Additionally, the exhaust port 31'of check valve 32, is connected viacoupling 38 to the input port 40 of a similar check valve, 42.

The exhaust port 44 of check valve 42 is connected via coupling 46 tothe intake port 47 of fluidic switch 48. The fluidic switch 48 is a twoposition switch. One position of switch 48 is as shown in FIG. 2,wherein the plunger 50 is positioned below the exhaust port 52. Thesecond position of switch 48 is when the plunger 50 is drawn to the topof bore 54, such that plunger 50 is now above exhaust port 52.

The exhaust port 56 of switch 48 is connected via coupling 58 to theinput port 60 of line filter 62. The line filter 62 has a filter element64, which typically is suitable for filtering particles on the order ofp. meters. The exhaust port 66 of filter 62 is coupled to a variablelength of pneumatic tubing 12 through coupling 68.

The pneumatic tubing 12 typically, is made from a polyethylene, ofsuitable strength to withstand pressures of at least 150 psig. The otherend of the variable length tubing 12 is connected via coupling 70 to theinput port 72 of the relief valve 16.

Input port 72 is connected to an internal port 74 within the valve I6,by a duct 76. The internal port 74 is capped by a diaphragm 78 which isspring biased against the port 74 by the action of spring 80. The springpressure maintaining the diaphragm 78 sealed against internal port 74 isadjusted by means of screw 81. Leakage oriface 82 connects the duct 76to the outside air. The oriface 82 might have a diameter 0.001 inch to0.003 inch diameter. This introduces sufficient leakage to provideprotection against an unintended buildup or retention of gas pressure inthe valve, tubing network. In this way only the operator performing thepressurization procedure from the beginning can initiate the ignition.The exhaust port 28 of relief valve 16 is connected via coupling 84 tothe pneumatic tubing 22, which in turn connects the valve. tubingnetwork to the fluidic conversion device 18.

Referring to FIG. 3 there is shown in detail the fluidic conversiondevice 18 embedded in propellant 24. The fluidic conversion device 18 isthe key component in the fluidic ignition system. The fluidic device 18is similar in construction and operation to the device described in U.S.Pat. No. 3,630,150 and 3,630,151. However, the designs described in theaforementioned patents were found to be suitable for use with highpressure. other than air. gas supplies and as such are not suitable forthe application envisioned here, viz, actuating a fluidic conversiondevice with a low pressure air supply.

For its application in an ignition system for a rocket motor. it isdesirable to manufacture the fluidic conversion device 18 from acombustible plastic material such that the device I8 burns up in theheat of the ignited propellant 24. This eliminates any possibility ofclogging of the rocket motor exhaust nozzle 84 (see FIG. 1). A suitablematerial. which also minimizes heat transfer loss to thereby contributeto a fast reaction time. was found to be a glass-filled epoxymanufactured by the Hysol Company and marketed under the trade name,MGSF. The conversion device may be molded together with the propellant24, or it may be installed or embedded in the propellant after thepropellant is packed or while the propellant is being packed.

The fluidic conversion device 18, basically consists of two essentialparts. a resonance tube (hollow cavity closed at one end) 85 and anexcitation nozzle 86. The nozzle of the fluidic conversion device 18 isa simple,

convergent type designed to produce the proper jet cell structure. ashereinafter described, necessary to obtain resonant heating in tube 85.The nozzle diameter 88 and the pressure ratio Pg/P across the nozzleinfluence the length of the jet cells, so that these two parameters maybe utilized to determine the proper separation distance 90, between thenozzle 86 and the resonance tube 84. It is the location of the opening91 of the resonance tube in a particular jet cell as hereinafterdescribed which gives rise to the heating efi'ect. The nozzle diameter88 also determines the rate at which the supply pressure in pneumatictubing 12 drops when the relief valve 16 is opened. If the pressuredrops too quickly, i.e., too large a nozzle diameter, resonance heatingwill take place for a time too short to develop ignition temperatures. Asuitable pressure ratio across the nozzle, P /P on the order of 3 to 4,has been found to be required to give a suitable flow pattern with theappropriate jet cell structure. Experimentation resulted in theselection of a nozzle diameter 88, of 1.2 mm and a separation distance90, of 2.0 mm.

With regard to the resonsnce tube 85, the preferable geometry whererelatively low air pressure is the actuating force, was discovered to bethe stepped configuration as shown in FIG. 3. This compares with thecylindrical and tapered configuration of the devices described in theaforementioned patents. A preferable tube length from the opening of thecavity 91, to the closed end 92, might be on the order of 10 mm. Theinternal diameter of the resonance tube 85 might preferably vary in thestepped fashion from 1.5 mm at the open end of the tube to 0.5 mm at theclosed end. The length and diameter of the tube can be varied dependingupon the maximum temperature sought to be achieved at the closed end andupon the time required to reach that temperature.

Since resonant heating is a flow phenomenon, no resonant heating ispossible without some means of venting. The vent tube 26, allows the airbeing discharged from the tube 85 to leave the fluidic device 18. Ashereinabove mentioned. one parameter which determines the location ofthe jet cell structure is the pressure ratio across the nozzle, P /PWith an unrestricted vent where P P,,,,,,, the ratio is simply Pu/PWhere the fluidic device 18 is embedded in a propellant 24, then thevent area is finite. This results in P being greater than P so that thepressure ratio is reduced. Thus, the vent tube diameter and length mustbe considered. A suitable vent tube diameter 94 was found to be 6.4 mm.Additionally, it was found that a tube length of 1 meter could beattached to the device without reducing the pressure ratio below thatneeded to insure ignition.

End 92 of resonance tube 84 opens into a conical, cylindrical shapedopening 95. The cylindrical portion 96 of the opening contains apropellant igniter suitable to activate the propellant 24. In rocketmotor applications BKNO boron potassium nitrate, would be a suitablepropellant igniter. The BKNO is available commercially in cylindricalpellet form, where each pellet is 3 mm in diameter and 2.5 mm long.

In order that the heat generated at the end of the resonance tube ignitethe propellant igniter in cylindrical portion 96, it has been found thata propellant igniter interface 98, be used between the end 95 and thepropellant igniter in cylindrical portion 96. This material is packedinto the conical section 100 between end 95 and the BKNO, and therebycloses off the otherwise open end 95. It has been found that in order toignite the propellant igniter, BKNO the interface material must be suchas to produce a hot particulate matter upon its ignition. What is neededis a pyrotechnic which will ignite at the expected resonance tube endtemperature and not be dispersed by the disruptive effect of theoscillating air at the end of the tube, 95. An interface material foundsuitable for the described application might be nitrocellulose which hasan ignition temperature of about 170 C.

In operation, when the operator draws the pump handle upward, checkvalve 32 opens and air is drawn in through intake port 36 into the pump10. On the downstroke the air contained in the pump is under a pressuregreater than the atmospheric pressure and as such closes valve 32.Instead, the air forces open check valve 42 allowing the air containedin the air pump 10 to enter the balance of the valve, tubing network. Tofacilitate the time for pumping this system up to the desired pressure,valves 32 and 42 have a cracking or opening pressure which may be on theorder of 0.3 psi.

With the fluidic switch 48, in the position indicated in FIG. 2, the airchanneled through the check valve 42 next proceeds through line filter62. Depending on the size ofthe filter element 64, dust particles andother extraneous matter contained within the pumped air are filteredout. This prevents these particles from clogging the igniter nozzle, 86.

Next, the pumped air passes to the variable length, pneumatic tubing 12.This length of tubing forms a gas supply volume sufficient to maintainthe required pressure ratio across the nozzle 86 of fluidic device 18,for a time sufficient to sustain resonant heating until the propellantigniter/propellant charge is ignited. Based on the igniter time/ignitiontemperature characteristics cited above, viz. a nozzle diameter of L2mm, a separation distance of 2.0 mm, a propellant igniter interface,ignition temperature of 170 C, and a time to ignite requirement of 2seconds, a 100 meter line with an internal diameter of 6.4 mm was foundto be adequate. By varying the conditions just mentioned the volumecharacteristics of the pneumatic tubing would have to be varied as wellto fit the requirements of a particular configuration.

The operator continues to pump the air pump 10 until the pressure in thepneumatic tubing 12 reaches the threshold level of relief valve 16. Forthe combinations set out above it has been found suitable to set theopening pressure of relief valve 16 at 72 psi. Once the relief valve isopened, the supply pressure in pneumatic tubing 12 decays according tothe following equation: P P, exp V'yR To (2/'y+ l)'y+ 1 7yl'(A*/V) I)where:

P,, the pressure at any ,time after the valve 16 opens,

P, the initial pressure in tubing 12,

y the ratio of specific heats (C,,/C,.) for the gas used,

R the gas constant T, the supply flow temperature A* the nozzle area ofthe exit of excitation nozzle V volume of transfer tubing 12,

I time When the valve opens, P must continue to be of sufficient levelso that sufficient pressure is maintained across the excitation nozzle86 such that resonant heating is sustained in resonant tube for a periodof time t, sufficient to ignite the propellant igniter interface 98. Therelief valve 16 is designed such that it does not close again until thepressure drops to below 10 percent of the opening pressure. According tothe above equation this insures that it will stay open long enough toinsure ignition.

This ability of the relief valve 16 to maintain itself opened until thesupply tube 12 pressure drops to greater than 10 percent of its openingpressure is due to a unique utilization of the standard type valve.Where normal utilization calls for exhaust port 28 to be used as theintake port and input port 72 connected to duct 76, to form the exhaustport, this invention interchanges the position of the two ports. Withthe air not entering port 72 and, thereafter, flowing into duct 76, aninitial pressure P is exerted on that portion of diaphragm 78 whichcovers the opening of duct 76. When the relief valve opens, diaphragm 78is pushed back from the opening of duct 76. The air in supply tubing 12,thereafter fills the volume of valve 16, exit port 28 and pneumatictubing length 22. At this time, therefore, the total force being exertedon diaphragm 78 increases by the ratio of the total area of thediaphragm surface to the area of the open end of duct 76. Thismultiplication effect, therefore, keeps the cover open until the airpressure drops to a level such that the pressure times the total area ofthe diaphragm is equal to the force first required to uplift thediaphragm from the opening of duct 76. Through proper design, this willenable the pressure to be maintained across the excitation nozzle 86 forthe period of time needed to raise the propellant igniter interface 98,to the required temperature.

The pressurized air is then carried to the excitation nozzle 86 offluidic device 18 by the pneumatic tubing 22.

As hereinabove mentioned, the fluidic device 18 consists of twoessential parts, the resonance tube 84 and the excitation nozzle 86.This device functions when the open end of the resonance tube 84 isplaced in the compression region of the free jet emanating from thenozzle 86. When the flow emerges from the nozzle, it accelerates tosupersonic-speed and then readjusts to subsonic speed by compressionthrough a shock wave. The process creates a series of diamond shapedcells, a b c def, c b c d e d, etc. of alternate supersonic and subsonicflow, see FIG. 4. The cells or conical shock waves intersect the jetaxis 102 throughout the length of the jet. A plot of a typical staticpressure distribution along the axis of the jet is also shown in FIG. 4.it can be seen that the pressure rises in the conical fronts of thediamonds and drops in the divergent portions to a minimum at theintersections, a f and c d. It was discovered that by placing the openend 91 of resonance tube 85, in the conical section, a b efor c b e d,of the diamond shaped cells, a self-sustaining oscillation of thepressurized gas occurs within the tube.

Although there is continuous flow into and out of the resonant cavity, aportion of the gas remains trapped at the closed end 95. There it issubjected to a succession of waves producing periodic compression andrarefaction of the gas. This periodic compression and expansion of thegas produces irreversible temperature increases at the end of the cavitywhich raises the end wall temperature to a point sufficient to ignitepyrotechnic materials such as nitrocellulose.

Once the propellant igniter interface is ignited, a hot particulatematter is created sufficient to ignite the propellant igniter BKNO whichin turn ignites the main propellant 24.

if it is desirous to abort a given firing, fluidic switch 48 can beactuated by depressing the plunger 50 such that it drops below opening104. This vents any of the air built up throughout the valve, tubingnetwork to the outside, through exhaust port 52.

Whereas the above disclosure discussed a system wherein an operatormanually brought the system up to the threshold pressure, it is to beunderstood, of course, that where time to fire must be relatively rapid,air pump 10 may be suitably replaced by a pressurized aerosol can, orautomatic pump arrangement.

Additionally. the principles of the subject invention, in addition tobeing used as a first stage ignition system as described above, may beutilized as part ofa suitable airborne device so as to provide themechanism for second stage firing, etc. A fluidic type computer could beprogrammed to divert a pressurized gas, conceivably the air outside therocket, to a conversion device similar to device 18. This computer wouldbe programmed to effect this diversion at an appropriate time, suitablefor second staging.

Although the principles of the invention have been described in anignition system for the firing of a sounding rocket, it should beapparent to those skilled in this art that the principles of theinvention can be readily adapted to the commercial explosive market tothereby provide a safe. effective means for detonation of explosivessuch as dynamite or the like.

Whereas the fluidic conversion device 18 has been described as beingconstructed from a low heat transfer material such as Hysol Company'sMGSF. it is to be understood that the device 18 can also be molded, inits entirety from nitrocellulose. This eliminates the need for theconical section 100 of opening 95, requiring only cylindrical section96. The BKNO is packed in this cylindrical portion 96 as before. Thewall thickness between tube 85 and section 96 might be on the order of0.050. Now when the resonance takes place the heat transfercharacteristic of the nitrocellulose is sufficiently low to allow forthe end wall temperature to rise to 170 C in the required time andthereby ignite the nitrocellulose. This will. in turn. ignite the BKNOensuring ignition of the propellant 24.

It can also be appreciated that changes in the above embodiment can bemade without departing from the scope of the present invention, and thatother variations of the specific construction disclosed above can bemade by those skilled in the art without departing from the invention asdefined in the appended claims.

What is claimed is:

1. An apparatus for igniting a remotely located explosive charge whichcomprises:

A. means remotely located with respect to said explosive charge forgenerating a threshold gas pressure said means comprising: (a) an airpump having an exhaust port; (b) a pair of check valves with the exhaustport of one of said check valves connected to the exhaust port of saidair pump; and (c) means for storing pressurized gas. the input port ofsaid storage means being connected to the exhaust port of the second ofsaid check valves said storage means including a relief valve having anintake port and an exhaust port, said relief valve being calibrated toopen at the threshold pressure and to re main open to predetermined timethereafter with the intake port of said relief valve including a leakageorifice for venting the intake port to the outside air to provideprotection against accidental buildup or retention of gas pressure insaid storage means, a length of pneumatic tubing of a storage volumesufficient to maintain the pressure of the stored gas at or near thethreshold level for a predetermined period of time, and a length ofplastic tubing connected to the exhaust port of said relief valve;

B. a fluidic conversion device embedded in said explosive charge, saidfluidic device including (a) a convergent nozzle pneumatically coupledto said plastic tubing; (b) a resonance tube, the open end of which ispositioned coaxially with and at a predetermined distance from the exitport of said convergent nozzle, said fluidic device further including(c) a venting tube positioned so as to vent the space between said exitport and said opening said venting tube having a prescribed diameter andlength which together with a predetermined ratio such that said fluidicdevice converts the energy stored in said pressurized gas to rise intemperature at the other end of said resonance tube; and (d) apropellant interface interposed between the other end of said resonancetube and said explosive charge, said propellent interface beingresponsive to a rise in temperature in said other end so that it igniteswhen the temperature reaches a prescribed ignition temperature andconsequently causes the ignition explosive charge.

2. The apparatus of claim 1 wherein said threshold pressure generatingmeans further comprises:

A. a two position fluidic switch; and

B. a line filter serially connected to said fluidic switch;

C. said serial connection interposed between the exhaust port of saidsecond check valve and the intake port of said storage means;

D. said two position switch having a first position whereby the exhaustport of said second check valve is connected to the intake port of thestorage means and a second position whereby said storage means is ventedto the outside air, thereby prohibiting a pressure buildup in saidstorage means.

3. The apparatus of claim 2 wherein said fluidic conversion device ismanufactured from a combustible plaster material.

4. The apparatus of claim 3 wherein said fluidic device further includesa cavity:

A. said other end of said resonance tube opening into said cavity,wherein said cavity contains said propellant interface;

B. said propellant interface packed into said cavity to thereby closeoff said other end of said resonance tube.

5. The apparatus of claim 4 wherein said propellant interface includes:

A. a pyrotechnic material positioned closest to said other end of saidresonance tube; and

B. a propellant igniter material;

9 10 C. said propellant igniter material positioned bewith thelongitudinal axis of said resonance tube and tween said pyrotechnic maria n i xp i positioned a predetermined distance from said other charge.end; 6. The apparatus of claim wherein said pyrotechnic wherein Saidother end is a closed end, and mammal mtroceuulose 5 B. wherein saidcavity contains said propellant inter- 7. The apparatus of claim 6wherein said propellant igniter material is BKNO 8. The apparatus ofclaim 2 wherein said tluidic conversion device is manufactured from apyrotechnic ma- Interface conslsts of a Propellant lgnlter maleflali L w11. The apparatus of claim 10 wherein said propel- 9. The apparatus ofclaim 8 wherein said fluidic de- 1am gn material is avice furtherincludes a cavity, said cavity axially aligned face.

10. The apparatus of claim 6 wherein said propellant.

1. An apparatus for igniting a remotely located explosive charge whichcomprises: A. means remotely located with respect to said explosivecharge for generating a threshold gas pressure said means comprising:(a) an air pump having an exhaust port; (b) a pair of check valves withthe exhaust port of one of said check valves connected to the exhaustport of said air pump; and (c) means for storing pressurized gas, theinput port of said storage means being connected to the exhaust port ofthe second of said check valves said storage means including a reliefvalve having an intake port and an exhaust port, said relief valve beingcalibrated to open at the threshold pressure and to remain open topredetermined time thereafter with the intake port of said relief valveincluding a leakage orifice for venting the intake port to the outsideair to provide protection against accidental build-up or retention ofgas pressure in said storage means, a length of pneumatic tubing of astorage volume sufficient to maintain the pressure of the stored gas ator near the threshold level for a predetermined period of time, and alength of plastic tubing connected to the exhaust port of said reliefvalve; B. a fluidic conversion device embedded in said explosive charge,said fluidic device including (a) a convergent nozzle pneumaticallycoupled to said plastic tubing; (b) a resonance tube, the open end ofwhich is positioned coaxially with and at a predetermined distance fromthe exit port of said convergent nozzle, said fluidic device furtherincluding (c) a venting tube positioned so as to vent the space betweensaid exit port and said opening said venting tube having a prescribeddiameter and length which together with a predetermined ratio such thatsaid fluidic device converts the energy stored in said pressurized gasto rise in temperature at the other end of said resonance tube; and (d)a propellant interface interposed between the other end of saidresonance tube and said explosive charge, said propellent interfacebeing responsive to a rise in temperature in said other end so that itignites when the temperature reaches a prescribed ignition temperatureand consequently causes the ignition explosive charge.
 2. The apparatusof claim 1 wherein said threshold pressure generating means furthercomprises: A. a two position fluidic switch; and B. a line filterserially connected to said fluidic switch; C. said serial Connectioninterposed between the exhaust port of said second check valve and theintake port of said storage means; D. said two position switch having afirst position whereby the exhaust port of said second check valve isconnected to the intake port of the storage means and a second positionwhereby said storage means is vented to the outside air, therebyprohibiting a pressure buildup in said storage means.
 3. The apparatusof claim 2 wherein said fluidic conversion device is manufactured from acombustible plaster material.
 4. The apparatus of claim 3 wherein saidfluidic device further includes a cavity: A. said other end of saidresonance tube opening into said cavity, wherein said cavity containssaid propellant interface; B. said propellant interface packed into saidcavity to thereby close off said other end of said resonance tube. 5.The apparatus of claim 4 wherein said propellant interface includes: A.a pyrotechnic material positioned closest to said other end of saidresonance tube; and B. a propellant igniter material; C. said propellantigniter material positioned between said pyrotechnic material and saidexplosive charge.
 6. The apparatus of claim 5 wherein said pyrotechnicmaterial is nitrocellulose.
 7. The apparatus of claim 6 wherein saidpropellant igniter material is BKNO3.
 8. The apparatus of claim 2wherein said fluidic conversion device is manufactured from apyrotechnic material.
 9. The apparatus of claim 8 wherein said fluidicdevice further includes a cavity, said cavity axially aligned with thelongitudinal axis of said resonance tube and positioned a predetermineddistance from said other end; A. wherein said other end is a closed end,and B. wherein said cavity contains said propellant interface.
 10. Theapparatus of claim 6 wherein said propellant interface consists of apropellant igniter material.
 11. The apparatus of claim 10 wherein saidpropellant igniter material is BKNO3.